Extreme pressure lubricants



United States Patent Office 3,313,398 Patented May 9, 1967 3,313,888 PRESSURE LUBRE'CANTS John I. Plemich, Whiting, and James W. Gaynor, Valparaiso, 1nd,, assignors to Standard Oil Company, Chicage, TEL, a corporation of Indiana No Drawing. Filed Get. 15, 1963, Ser. No. 316,440 5 Claims. Cl. 25232.7)

This invention relates to improved pressure (E.P.) lubricants and the method of preparing same. It is pan ticularly concerned with improvements in such lubricants containing lead naphthenate and zinc dialkyl dithiophos phate.

The use of the lead naphthenate and the zinc salt together in a lubricant impart valuable extreme pressure properties to the lubricant enabling it to be adopted in services where high load-bearing duties are encountered. The additive of this invention, consisting essentially of lead naphthcnate soap and zinc salt of a dialkyl substituted dithio-phosphoric acid, is especially useful under conditions in which the gears are exposed to moist dust laden atmosphere, such as are the gear teeth of mine crusher apparatus.

The zinc salts of dialkyl diesters of dithiophosphoric acid, or, as they are more commonly called, zinc dialkyl dithiophosphates, are well known in the lubricating oil art. Methods of preparing these salts generally involve reacting phosphorous pentasulfide with an alcohol or mixture of alcohols to form a dithiophos-phoric acid, which is then reacted with zinc oxide to form the dialkyl dithiophosphate. The preferred zinc dialkyl dithiophosphat es are prepared from one or more primary or secondary alkyl alcohols having from about 3 to about 18 carbon atoms in the molecule, with at least one of the alcohols desirably containing at least about 8 carbon atoms. When improved stability to thermal decomposition is important, the alkyl groups of the dialkyl substituted dit'niophosphoric acids are derived from primary alcohols. The higher carbon containing (above C alkyls enhance oil solubility, but since they are derived from C and higher alcohols, are somewhat more costly than the C and lower alkyls derived from the C and lower alcohols. Hence, combinations of C and lower primary and/or secondary alcohol plus C and above alcohol are selected at a ratio of the C and higher to C and lower to suit the balance between economics and solubility as the particular situation dictates.

Examples of primary alkyl alcohols and of secondary alkyl alcohols suitable for use in the preparation of the zinc dialkyl dithiophosphate are tabulated below.

Primary alcohols: n-Pr-opyl Iso-butyl n-Butyl Oxo-amyls Isoamyl (isobutyl carbinol) lsooctyl Oxo-octyl n-Decyl n-Dodecyl (lauryl) Z-ethyl-l-hexanol Stearyl Secondary alcohols:

Isopropyl (dimethyl carbinol) Sec-butyl (methyl ethyl carbinol) Sec-amyl (methyl-n-propyl carbinol) Sec-n-octyl (methyl-n-hexyl carbinol) Methyl isobutyl carbinol Sec-isohexyl A good source of primary alcohols is the x0 process for preparing primary branched chain alcohols. The

so-called oxo alcohols are made by a hydroformylation process which involves the catalytic reaction of a monoolefin with carbon monoxide and hydrogen, and the hydrogenation of the resultant aldehydes. to form primary branched chain alcohols. The oxo alcohols from C to C olefins are particularly suitable as alcohols for the formation of dialkyl dithiophosphoric acids to be converted to the zinc salts. Such oxo-alcohols can be used in admixture with isobutyl alcohol or oxo-amyl alcohols and reacted with P 8 Also, the foregoing C to C oxoalcohols can be reacted separately with P 8 and admixed in the selected ratio (balance of economics and oil solubility) with the dialkyl dithiophosphoric acids from P 8 reaction with isobutyl alcohol and/or oxoamyl alcohol mixture (principally primary C alcohol).

A preferred method of preparing zinc dialkyl dithiophosphates comprises heating the rimary alcohol or alcohols to a temperature of about F. to F. and as rapidly as possible introducing into the heated alcohol a slurry of the P 3 in a suitable hydrocarbon oil diluent, for example a 5W Motor Oil Base. After the required amount of the P 8 has been added, the mixture of alcohol and P 8 slurry is heated to about 200 F. and maintained at this temperature until reaction between the alcohol and the P 8 is completed. To form the zinc salt of the thiophosphoric acid, a slurry of zinc oxide in the SW motor oil base, or other desired light hydrocarbon oil diluent, is introduced into the P s alcohol reaction mixture maintained at a temperature of about 135-140 F. and the resultant salt then dehydrated by heating at or above the boiling point of water, about 210 F., with inert gas blowing. After continued inert gas blowing, say at about 210 F. until the product is essentially free of H 8 and H 0, the product is, if desired, clay or celite-filtered at about 210 F. to remove unreacted solids.

In the preparation of the dialkyl dithiophosphoric acid, the alcohol and the P 5 are reacted together in mole ratios of from 1.8:1 to about 2.2:1. In the preparation of the zinc salt of the thio acid, the zinc oxide and the thio acid are used in mole ratios of from 0.4:1 to about 0.7:1, respectively.

For use in E. P. lubricants according to the present invention, zinc dialkyl dithiophosphates may be employed in a concentration ranging from about 0.1 to about 2% by weight in the final oil.

Hydrocarbon or mineral lubricating oils which form the base stocks for the present lubricants are ordinarily in the higher viscosity ranges commonly employed in gear lubricants, e.g., from about 45 to about S..S.U. at 210 F. and preferably from about 75 to about 110 S.S.U. at 210 F. In additional to the zinc dialkyl dithiophosphate and lead naphthenate, the lubricant may also contain elfective amounts of various other lubricant additives such as antioxidants, detergents, antifoam additives, etc.

DEFOAMIN G AGENTS Defoaming agents are well known. These agents finely dispersed in the formulated oil base elfectively suppress or prevent the frothing and foaming of hydrocarbon oils, preferably without substantially modifying the desirable properties of the oils. Especially useful are organo-silicon oxide and hydroxide condensation products, such as those described in US. Patents 2,416,513 and 2,416,504. Such agents are effective lubricating oils defoaming agents in concentrations as low as 0.5 part to 10 or more per million.

The amount of lead naphthenate employed herewith may vary over a relatively wide range depending upon a variety of factors, as, for example, the end use of the lubricant. Lubricants with lead naphthenate contents of from 0.5 to about 10% or more have been employed. It

is preferred to use the lead naphthenate and zinc salt in a ratio of about to 1 for it is at these ratios that results beyond additive (sum of the effect of zinc salt plus effect of lead soap) are achieved. Basic lead naphthenate is available as a commercial product containing about 3035 weight percent lead and is soluble in mineral oils.

Example I To demonstrate the markedly improved extreme pressure properties of a lubricant containing both lead naphthenate and zinc dialkyl dithiophosphate, various lubricant samples were prepared. The samples were subjected to the Timken Test to determine their ability to withstand heavy loads.

The first two samples contained 5 percent by weight basic lead napthenate (30% lead) in a blend of solvent extracted SAE 20 and SAE 40 mineral oils to which had been added 3 parts per million silicon polymer defoaming agents. Sample 1 contained 1 percent by weight of zinc dialkyl dithiophosphate prepared from a mixture of 30% propyl alcohol and 70% C alcohol, while Sample 2 contained no zinc additive. The samples were then subjected to the Timken Test.

The Timken Test referred to above is well known to those skilled in the art. The test basically consists of submitting lubricants to the conditions of a Timken testing machine to obtain comparative loadbearing capacities of lubricants, exceedingly valuable information with respect to the potential commercial value of extreme pressure lubricants. The Timken machine and test are fully described in the Journal of the Institute of Petroleum, 32, pp. 209-210 and 220-222 (1946).

The following results were obtained in the various tests:

TEST RESULTS Zinc Dialkyl Dithiophos- Lead Naphthenate, Lbs. Pass Lbs. Fail phate, Percent Percent Sample 1 5 None 5 *In none of four runs could passing result be obtained at the 10 pound load level.

Example 11 A sample was prepared to show the extreme pressure characteristics of Zinc dialkyl dithiophosphate alone. This sample contained 1 percent by weight of zinc dialkyl dithiosphosphate prepared in the same manner as above. This exhibits the following results on the Timken Tests:

TEST RESULTS Sample 3 Zinc dialkyl dithiophosphate percent 1 Lead naphthenate None Pounds pass 33 Pounds fail 4 Although zinc dialkyl dithiophosphate does impart some extreme pressure qualities to a lubricant when used alone lead napthenate alone does not. The interaction of these two constituents to give a lubricant a relatively high extreme pressure value, much beyond what would be expected from either alone, is, therefore, indeed remarkable.

The extreme ressure additives of this invention may be prepared as concentrates, the concentrate containing from about 40 to 65 weight percent of a composition consisting essentially of lead naphthenate and zinc dialkyl dithiophosphate in a suitable diluent such as the above-mentioned high viscosity mineral lubricating oils. Again, the effective weight ratio of lead naphthenate to zinc dialkyl dithiophosphate of about 5 to 1 should be maintained. The concentrate may also contain other additive components for other purposes, such as the above-mentioned defoaming agents.

From the foregoing presentation, it is clear that the extreme pressure characteristics of hydrocarbon lubricants containing zinc dialkyl dithiophosphate are vastly improved when the lubricants also contain lead naphthenate.

We claim:

1. An extreme pressure lubricant composition comprising a major amount of a hydrocarbon lubricating oil having a viscosity in the range of about 45 to about 180 S.S.U. at 210 F., from about 0.5 to about 10 weight percent of a lead naphthenate, and from about 0.1 to about 2 weight percent of a zinc salt of a dialkyl diester of dithiophosphoric acid having from about 3 to about 18 carbon atoms in each dialkyl radical; wherein the Weight ratio of lead naphthenate to Zinc salt is about 5 to 1.

2. The composition of claim 1. wherein the Zinc salt is prepared from a mixture of dialkyl dithiophosphoric acid which are derived essentially from alcohols of 3 carbon atoms and 10 carbon atoms; wherein the 10 carbon atom alcohols comprise about mole percent of said mixture.

3. The composition of claim 2 which contains about 5 weight percent lead naphthenate.

4. The composition of claim 3 to which is added 3 parts per million of a defoaming agent.

5. An extreme pressure hydrocarbon lubricating oil concentrate consisting essentially of a lubricant and from 40 to 65 weight percent of a composition consisting essentially of lead naphthenate and a Zinc salt of a dialkyl diester of a dithiophosphoric acid having from about 3 to about 18 carbon atoms in each dialkyl radical; wherein the weight ratio of lead naphthenate to zinc salt is about 5 to 1; and said concentrate is capable of dilution with a hydro carbon lubricating oil to form an extreme pressure lubricant.

References tilted by the Examiner UNITED STATES PATENTS 2,220,843 11/1940 Johnson 252-486 X 2,416,504 2/1947 Trautman et a1 252-496 2,689,220 9/1954 Mulvany 252-327 3,000,822 9/1961 Higgins et al. 252-327 3,013,970 12/1961 Mastin 252-32] 3,211,653 10/1965 OHalloran 252-327 X 3,222,280 12/1965 Wolfram et a1 252-327 DANIEL E. WYMAN, Primary Examiner.

P. P. GARVIN, Assistant Examiner. 

1. AN EXTREME PRESSURE LUBRICANT COMPOSITION COMPRISING A MAJOR AMUNT OF A HYDROCARBON LUBRICATING OIL HAVING A VISCOSITY IN THE RANG OF ABOUT 45 TO ABUT 180 S.S.U. AT 210*F., FROM ABOUT 0.5 TO ABOUT 10 WEIGHT JPERCENT OF A LEAD NAPHTHENATE, AND FROM ABOUT 0.1 TO ABUT 2 WEIGHT PERCENT OF A ZINC SALT OF A DIALKYL DIESTER OF DITHIOPHOSPHORIC ACID HAVING FROM ABOUT 3 TO ABOUT 18 CARBON ATOMS IN EACH DIALKYL RADICAL; WHEREIN THE WEIGHT RATIO OF LEAD NAPHTHENATE TO ZINC SALT IS ABOUT 5 TO
 1. 